Renaissance treasures 

"At first the men were accustomed to donning masks, mimicking the ladies who customarily went about masked during the celebration of the first of May. And thus adopting the custom of the ladies and youths, they donned costumes and sang dance songs." That's from an account of mid-15th-century Florence, published by A.F. Grazzini.

When he became Florence's ruler in 1469, Lorenzo de' Medici transformed this scene into a full-blown carnival season. New diverse songs would be composed; masked men selling pastries would sing. What does all this have to do with 21st-century Rochester? More than you might think.

Lorenzo de' Medici invited a composer from Flanders (North Belgium), Heinrich Isaac (1450-1517, pronounced HI-nrik ee-SOK), to take up a position in Florence. Like no one before him, and few after him, Isaac could compose almost any style: German "Tenorlieder," French chansons, Latin motets, and --- of course --- Italian carnival songs.

"Isaac's music bursts with a seemingly spontaneous flow of melodic and rhythmic ideas," says Eastman School musicologist Patrick Macey, "and this playful quality suggest to me that he must have been highly proficient as a singer-improviser."

Rochester is lucky to boast an a cappella choir devoted expressly to Renaissance music: Musica Spei (Music of Hope). This year marks Musica Spei's 10th anniversary, and it has chosen the music of Isaac to sing in its anniversary concert.

Musica Spei started in the mid-'90s. Local singers would gather at Saint Anne Church to sight-sing through Renaissance music. At first, "I warned the group not to expect more than 20 to 25 people in the audience," says singer Steve Marcus. "That it would take a long time to build an audience for such esoteric music. We were astonished to find large, enthusiastic audiences at each performance."

Musica Spei gains its repertoire from the vast resources of Rochester's Sibley Music Library, which houses "the musical equivalent of countless undiscovered da Vincis, Michelangelos, Renoirs and other masterpieces," Marcus says.

In 1492, while Columbus was discovering America, tragedy struck in Florence. A lightning bolt brought the ornate cathedral dome crashing to the floor. Lorenzo de' Medici died of gout just days later. Isaac lamented his patron's death by composing Quis dabit --- a work Musica Spei found "accessible on first reading," says singer and director Lynnette Blake. "The group loves the poignant sadness it expresses." They'll perform it at the concert.

Matters worsened in 1494. The remaining Medici family was banished. A puritanical Dominican friar, Giromalo Savonarola, seized Florence and instituted bonfires citywide to destroy carnival vanities: "women's hats, mirrors, wigs, dolls, perfumes... sculptures, cupids, playing cards, dice boards, chess pieces, lutes and other musical instruments," says one 1497 account.

Savonarola rejected Isaac's opulent sort of music, likening it to the voice of a calf or a howling dog whose words he couldn't understand. Isaac sought inspiration and support elsewhere, and found them in one of Europe's most powerful men: Hapsburg Emperor Maximilian I. For him, Isaac composed the nostalgic lyrical Innsbruck, Ich muss dich lassen, perhaps the most famous Renaissance song --- also to be performed at the concert.

It was for Maximilian's cathedral in Constance, Germany, that Isaac undertook one of the most ambitious music projects in all of history: Choralis Constantinus, three volumes of choral settings of the Catholic Mass.

For Renaissance composers, the Mass was the most ambitious genre. Typically Renaissance composers set to music the "Ordinary" --- the Mass text that is the same each day. Yet in Choralis Constantinus Isaac set the Mass Propers: the changing texts designated as "proper" for each of the major feast days. It's a total of 99 Mass settings, each one a multi-movement work overflowing with intricate detail.

Many believe Isaac's intricate structures influenced the innovative Viennese modern composer Anton Webern (who in 1909 prepared the first modern edition of Choralis Constantinus, volume II). Isaac's motet O decus, to be sung Saturday, shows why: It anticipates modern composers' fascination with additive processes and palindromes. In O decus, one voice sings a rising scale additively --- first singing the lowest first pitch, starting again but adding the second pitch, starting again but adding the third, and so forth --- what the 12 Days of Christmas carol does with gifts, it does with pitches. Then the process goes backwards.

When the Hapsburg Empire fell in WWI, the modern edition of Choralis Constantinus remained incomplete. Louise Cuyler picked up the torch in 1948. She prepared the modern edition of volume III and did her dissertation on it at Rochester's Eastman School.

As Musica Spei planned its anniversary, it approached Macey to "dust off a worthy but unknown piece of music," says Marcus. Macey suggested he'd prepare an updated edition of the Mass Propers for St. John the Baptist from Choralis Constantinus, volume II.

The update was needed because scholars in Webern's time didn't understand the intricacies of Isaac's notation. To save paper and "test the wits of singers," says Macey, Isaac omitted some voice parts, expecting singers to derive them from formulas they deciphered.

Musica Spei gave the world premiere on June 3 in Canandaigua. It was probably the only performance since Isaac's time and the only one outside of Constance Cathedral.

"I think the group is greatly enjoying the sense of wonder and discovery," says Marcus, "and the feeling that perhaps few people, if anyone, have ever heard or sung this music in recent times."

The repeat performance on Saturday is our chance to join the adventure.

Musica Spei's Isaac Project: Angels and Archangels, Saturday, June 11, 8 p.m., Saint Anne Church, 1600 Mt. Hope Avenue. Free. 742-1292, www.musicaspei.org.